linux-kernel - Re: [PATCH 02/14] dt-bindings: serial: Document sci bindings for the Renesas RZ/T2H (a.k.a r9a09g077) SoC

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Message-ID: <CAMuHMdXVLyY10AgqR8J9FHB5mKiPXSWZ04EkW5ykE6bDj6EGPA@mail.gmail.com>
Date: Mon, 10 Feb 2025 15:48:42 +0100
From: Geert Uytterhoeven <geert@...ux-m68k.org>
To: Biju Das <biju.das.jz@...renesas.com>
Cc: Thierry Bultel <thierry.bultel.yh@...renesas.com>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Jiri Slaby <jirislaby@...nel.org>, 
	Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley <conor+dt@...nel.org>, 
	Magnus Damm <magnus.damm@...il.com>, 
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, 
	"linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>, 
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>, 
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>
Subject: Re: [PATCH 02/14] dt-bindings: serial: Document sci bindings for the
 Renesas RZ/T2H (a.k.a r9a09g077) SoC

Hi Biju,

On Mon, 10 Feb 2025 at 15:46, Biju Das <biju.das.jz@...renesas.com> wrote:
> > From: Biju Das <biju.das.jz@...renesas.com>
> > > From: Geert Uytterhoeven <geert@...ux-m68k.org>
> > > On Mon, 10 Feb 2025 at 15:26, Biju Das <biju.das.jz@...renesas.com> wrote:
> > > > > From: Geert Uytterhoeven <geert@...ux-m68k.org>
> > > > > On Mon, 10 Feb 2025 at 14:19, Biju Das <biju.das.jz@...renesas.com> wrote:
> > > > > > > From: Geert Uytterhoeven <geert@...ux-m68k.org>
> > > > > > > On Wed, 29 Jan 2025 at 17:52, Thierry Bultel <thierry.bultel.yh@...renesas.com> wrote:
> > > > > > > > Document RZ/T2H (a.k.a r9a09g077) in SCI binding.
> > > > > > > >
> > > > > > > > Signed-off-by: Thierry Bultel
> > > > > > > > <thierry.bultel.yh@...renesas.com>
> > > > > > >
> > > > > > > Thanks for your patch!
> > > > > > >
> > > > > > > > --- /dev/null
> > > > > > > > +++ b/Documentation/devicetree/bindings/serial/renesas,rzsci
> > > > > > > > +++ .y
> > > > > > > > +++ aml
> > > > > > > > @@ -0,0 +1,100 @@
> > > > > > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > > > > > > +%YAML
> > > > > > > > +1.2
> > > > > > > > +---
> > > > > > > > +$id:
> > > > > > > > +http://devicetree.org/schemas/serial/renesas,rzsci.yaml#
> > > > > > >
> > > > > > > "rzsci" is IMHO a bad name, as SCI on RZ/T2 differs from the
> > > > > > > similar-named "SCI" (sometimes called "RSCI" or "SCIg") on
> > > > > > > RZ/A1H, RZ/A2M, RZ/G2L, RZ/V2L, and
> > > > > RZ/G3S (and most old SuperH SoCs).
> > > > > > >
> > > > > > > BTW, I believe the variant on RZ/T2 is also used on RZ/N2, RZ/V2H, and RZ/G3E?
> > > > > > >
> > > > > > > However, binding-wise, they all seem to be very similar.
> > > > > > > So perhaps you can just add this to the existing
> > > > > > > Documentation/devicetree/bindings/serial/renesas,sci.yaml?
> > > > > >
> > > > > > It is present in RZ/G3E as well.
> > > > > > RSCI supports sci, scif, i2c and spi that is the reason renesas,rzsci.yaml introduced.
> > > > >
> > > > > If you plan to add support for I2C and SPI, you will need
> > > > > different bindings under Documentation/devicetree/bindings/{i2c,spi}/.
> > > >
> > > > OK, I thought since it is a single IP, we need to use a single
> > > > compatible and instantiate appropriate device based on the device
> > > > property rather than separate SCI,
> > > i2c and spi compatible.
> > > >
> > > > Yes, I agree having different device compatible for same IP make
> > > > life easier, no need to add specific vendor property.
> > >
> > > I said "different bindings", not "different compatible values"!
> > >
> > > Cfr. "renesas,tpu" having bindings in both
> > > Documentation/devicetree/bindings/timer/renesas,tpu.yaml
> > > and Documentation/devicetree/bindings/pwm/renesas,tpu-pwm.yaml.
> >
> > Thanks for clarification. This is simple solution.
>
> But, here we need to decide, which channels to be used in SCI, I2C and SPI
> in SoC dtsi
>
> or
>
> Maybe define all the channels as sci as default and override it in board dts for
> I2c and spi based on customer use case??

The latter, please.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds